In a conventional cellular system, the network consists of macro cells having a coverage scope generally ranged from 1 km to 25 km, which is a large radius so that a strong transmission power is necessary. Usually, transmission antenna of a macro cell is erected above surrounding buildings, and there is no direct antenna used between transmission and reception. In order to meet requirement of high rate data communication in modern wireless communication, higher spectrum reuse rate can be achieved by cell splitting, such that the throughput per unit area is improved. In 3GPP standard, femtocell, also called as home base station, is proposed as a technical standard for improving efficiency of frequency utilization and enlarging indoor wireless coverage rate. With a general transmission distance ranged from 10 m to 50 m, femtocell is mainly used for residence or enterprise environment. Featured by e.g. low power consumption, low cost and small coverage, etc., femtocell attracts much attention from researchers and operators. Statistics shows that in China more than 70% of data communication and voice service is performed indoors. In addition, with generation of respective applications, communication bandwidth requirements increase gradually. Also, in view of urban construction and population concentration, it can be predicted that, in the near future, a large quantity of femtocells will be deployed in various buildings such as residential community or commercial blocks.
However, because one and the same fraction of spectrum is used among different femtocells and among femtocells and macro cells, when femtocells are deployed densely, serious co-channel interference will be generated among users of different femtocells and among users of femtocells and of macro cells. Co-channel interference will negatively influence on reliable transmission of wireless communication, and also reduce wireless transmission rate and system throughput. Therefore, a solution for reasonable spectrum allocation is required for suppressing interference of the above two kinds of heterogeneous network environments so as to improve frequency utilization rate and system throughput. Statistics shows that, top 10% of mobile users in a mobile network consume almost 90% of bandwidth resource of mobile internet. Due to the difference of bandwidth resource consumption, it is necessary to consider different bandwidth requirements of users in spectrum resource allocation. When most users are satisfied with basic bandwidth and another small part of users requires more spectrum bandwidth and data traffic, allocating spectrum resource in combination with user difference bandwidth requirements can allocate the whole resource of network effectively. Therefore, it is necessary to efficiently design a solution for allocating spectrum based on interference suppression and user difference bandwidth requirements in the field.
Currently, research on how to suppress co-channel interference among femtocell users and among femtocell users and macro cell users is rarely reported. In this field, it is difficult to solve the problem of how to suppress the above two kinds of interference by a solution of reasonably allocating spectrum resource and at the same time satisfying user difference bandwidth requirements.